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Can you be fat and healthy?

Apples and pears: We all come in different shapes and sizes - and being fat doesn't mean being unhealthy.

We all know that carrying too many extra kilos can up the risk of heart disease and Type 2 diabetes – so how come up to 30 per cent of us can be very overweight yet still have healthy hearts and healthy levels of blood glucose?

One possibility is the 'fit and fat' theory that suggests being physically active can protect us from chronic diseases even when we weigh too much. One effect of exercise, for instance is that it makes muscles use up more blood glucose for fuel – this can help ward off Type 2 diabetes by keeping blood glucose levels down.

How come up to 30 per cent of us can be very overweight yet still have healthy hearts and healthy levels of blood glucose?

"Studies also show that some obese people who aren't physically active are also unexpectedly free of problems like high blood pressure and high blood fats," he says.

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What's more, they're also insulin sensitive which means their body's insulin is doing a good job of keeping their blood glucose levels healthy - this is the opposite of insulin resistance, the common condition that means your insulin is struggling to keep the glucose in your blood under control and puts you in the running for diabetes.

"One of the differences that sets these healthier overweight people apart is whereabouts on the body they store their excess fat. In people whose insulin is working well fat is more likely to be carried around the hips and thighs rather than around the waist," explains Chen who's trying to find out why some obese people side step the insulin resistance that sets others up for diabetes.

The surplus fat that clings to hips and thighs is different to the fat that hugs the waistline. Called subcutaneous fat, it sits there under the skin doing nothing other than padding out your jeans. But fat around the waist is likely to be visceral fat which is bad news for two reasons, he says.

"One is that it secretes inflammatory chemicals that contribute to heart disease and diabetes, the other is that it releases fatty acids which can be harmful too – they end up being stored in the liver and muscles and this makes it harder for the body to keep blood glucose levels down," he says. "But overweight people whose insulin is working well tend to have less of this 'bad' fat. They might have a lot of fat around the arms, legs and hips but they're not storing it around the waist, so in terms of diabetes it's not a problem."

Having this visceral fat can give even a relatively slim person a higher risk of diabetes than someone who weighs more, but carries their extra kilos around the hips and thighs.

"People can be slim but still have this harmful fat around the waist – including some Asian people who tend to have a lower BMI yet still have visceral fat around the middle," Chen says.

But although some overweight people may be protected from diabetes and heart disease, they're not bulletproof – the extra weight is still going to increase the risk of osteoarthritis, for instance, by adding a burden to hips and knees, he adds.

"Whether there's less risk of cancer with healthier obese people isn't clear. So far we only know there's less diabetes and fewer deaths from heart disease – but we also know there's an increased risk of cancer from diabetes."

Dr Daniel Chen needs more volunteers for his research to find out why some overweight people are protected from diabetes - if science can find a way to identify obese people who are insulin-sensitive more resources can be directed to those who are obese and insulin-resistant too, he says.

If you have a BMI of 30 or more, are aged between 18 and 70 and live in the Sydney area or in NSW, he’d like to hear from you. Contact (02) 9295 8557 or d.chen@garvan.org.au. If you don't know your BMI, you can use the Better Health Channel's online calculator to work it out.

66 comments

Genetics have a lot to do with a person's tendency to develop Type 2 diabetes. I have a BMI in the healthy range (23.4), but Type 2 diabetes runs in my family. That's always been a good incentive for me to keep my weight down. My last blood test a couple of months ago showed a slightly elevated blood glucose. I've stepped up the exercise program in a bid to speed up my metabolism and lose a couple of kilos. Will that reverse the upward trend? I don't know, but I will give it my best shot. What else can I do when it's apparently in my genes to develop Type 2 diabetes?

Commenter

Nini

Date and time

November 14, 2012, 9:33AM

Hi Nini - it might be a good idea to ask an endocrinologist for some advice about this. However, there's quite a bit of evidence now that strength training improves blood glucose control in people with and without diabetes. There's some info on a recent study here http://www.sciencedaily.com/releases/2012/08/120806161816.htm It might also be worth getting a referral to an Accredited Exercise Physiologist who could give you expert advice on the best way to train to improve blood glucose control.

Commenter

Paula

Date and time

November 14, 2012, 9:52AM

Thanks Paula! I'll ask my GP next time I see her.

Commenter

Nini

Date and time

November 14, 2012, 10:19AM

BMI has nothing to do with the body fat you carry! the body fat we carry around our organs and underneat skin is the one that can harm our health! And it depends on what you eat, how much you eat and when you eat, regardless if you exercise or not! You can be fit and fat, but that doesn't translate to healthy either.

Commenter

fat expert

Date and time

November 14, 2012, 11:17AM

Fat expert, I realise that BMI has nothing to do with the percentage of bodyfat. I was just using it to indicate that I'm not overweight. I don't know what percentage of that weight is fat. I eat a healthy, low-saturated-fat diet, and I exercise. I was just trying to say that sometimes, no matter what you do, genetics play a big part in health outcomes.

Commenter

Nini

Date and time

November 14, 2012, 10:27PM

There is a lot of evidence that you can be fat and healthy. Check these references:

Here's another quote from Dr. Briffa forum - Pretty much every single chronic disease known to man is caused by chronically-elevated blood sugar, or at least clusters around the condition that has come to be known as the Metabolic Syndrome. It is very likely that people that are a little overweight are in better overall health because they are more likely to have good bloodsugar regulation (i.e., putting on some fat mass is the physiologically-normal and healthy reaction to elevated blood sugar). People who are extremely obese on the other hand, have likely developed some degree of insulin resistance, and therefore have chronically-developed the same poor blood sugar regulation as someone underweight.

BMI is not even a decent measure of weight class (check wikipedia for BMI). It was developed for 'population' measurement and is not even recommended for individual use.

Emily Banks: Basically because they both matter, the worst thing to be is fat and inactive, the best thing to be is slim and active, and if you are fat and active or slim and inactive, you are in-between those two.

Norman Swan: Right, I'm going a bit cross eyed here but I think I get what you're talking about.

Emily Banks: Basically the myth of fat and fit is busted essentially. What it means is that you can't offset the effect of being fat by being fit, but it does help.

Regards

Peter

Commenter

Peter

Location

Oz

Date and time

November 14, 2012, 11:19AM

I think the Flegal and Oprana studies might trump that. Lets not forget there are some powerful forces who want to make lots of CASH from this including medical professionals. A quote from Paul Campos book is that 'Obesity is a disease than can be treated for life with no known side effects' in other words a big money tree.

Commenter

John Holmes

Date and time

November 14, 2012, 12:57PM

Have a look at the research above (Thanks to Holmes). The most dangerous weight to be is underweight, the healthiest weight range is BMI 25-30 (overweight). The risk of death for normal BMI 20-25 is the same as being obese 30-35.I would have to conclude that being fit and overweight trumps being fit and slim.

However, before you start getting cooking extra pasta, remember these are correlations and not proof of causation! Changing one's BMI any significant amount long term is generally very difficult, and that includes slim people who try to put on weight.

http://www.nytimes.com/2007/05/08/health/08fat.html

Commenter

Gordon Rouse

Location

Yinnar South

Date and time

November 14, 2012, 4:40PM

Check out US masters sprinter Marty Krulee (M55-59)

He would be considered overweight, but can still run world class times for his age division (sub 12s for 100m)